Medicine & USMLE


Amino Acids
  1. Serine
  2. Asparagine
  3. Alanine
  4. Valine
  5. Leucine
  6. Isoleucine
  7. Phenylalanine
  8. Tryptophan
  9. Methionine
  10. Proline
  11. Glycine
  12. Threonine
  13. Cysteine
  14. Tyrosine
  15. Glutamine
  16. Aspartate
  17. Glutamate
  18. Histidine
  19. Lysine
  20. Arginine


Tyrosine is an amino acid abbreviated as the 3 letters Tyr, or the single letter Y. Its R-group consists of 1 carbon linkage to a phenol group, which is just an aromatic benzene ring with a hydroxyl or alcohol group attached to it. The hydroxyl group makes tyrosine polar or hydrophilic, meaning that it can dissolve in water. The hydroxyl group also reacts with phosphate, meaning tyrosine is one of the most commonly phosphorylated amino acids. Tyrosine is neutral or uncharged at physiological pH and it serves biologically as a precursor to many important hormones, including epinephrine and thyroid hormone.

Key Points

  • Tyrosine
    • Abbreviations
      • Tyr, Y
    • Chemical Structure
    • R-group: -CH2-phenol
      • Aromatic benzene ring
        • Aromatic compounds absorb UV light
      • Hydroxy group (-OH)
        • Phosphorylatable
        • Usually performed by tyrosine kinases; serve key steps in cell signaling (e.g. RTKs) and other functions
    • Polarity
      • Polar (water soluble/hydrophilic)
    • Charge at pH 7
      • Neutral (0)
    • Other Information
      • Precursor to catecholamines (e.g. Epinephrine) and some hormones (e.g. Thyroid Hormones)